Synthesis and reactivity of five- and six-coordinate hydrido(vinyl) iridium(III) complexes

The reaction of the dihydrido iridium(III) precursor [IrH₂(Cl)(PiPr₃)₂] (5) with internal alkynes RCC(CO₂Me) (R = Me, CO₂Me) afforded the five-coordinate hydrido(vinyl) complexes [IrH(Cl){(E)-C(R)CH(CO₂Me)}(PiPr₃)₂] (6, 7), via insertion of the alkyne into one of the IrH bonds. Compounds 6 and 7 are also accessible by careful hydrogenation of the alkyne iridium(I) derivatives trans-[IrCl{RCC(CO₂Me)}(PiPr₃)₂] (9, 10), the latter being prepared from in situ generated trans-[IrCl(C₈H₁₄)(PiPr₃)₂] and RCC(CO₂Me). UV irradiation of 6 (R = CO₂Me) led to the formation of the isomer [IrH(Cl){κ²(C,O)-C(CO₂Me)CHC(OMe)O}(PiPr₃)₂] (3) having the vinyl ligand coordinated in a bidentate fashion. While 6 reacted with acetonitrile and CO to afford the six-coordinate iridium(III) compounds [IrH(Cl){(E)-C(CO₂Me)CH(CO₂Me)}(L′)(PiPr₃)₂] (11, 12), treatment of 6 with LiC₅H₅ gave the half-sandwich-type complex [(η⁵-C₅H₅)IrH{(E)-C(CO₂Me)CH(CO₂Me)}(PiPr₃)] (13) by, the loss of one PiPr₃. The reaction of 3 with CO under pressure resulted in the formation of [IrH(Cl){(Z)-C(CO₂Me)CH(CO₂Me)}(CO)(PiPr₃)₂] (14) in which, in contrast to the stereoisomer 12, the two CO₂Me substituents are trans disposed.     

Antifungal triazole derivative triadimefon induces ectopic maxillary cartilage by altering the morphogenesis of the first branchial arch

BACKGROUND: The triazole derivative, triadimefon (FON), induces branchial arch abnormalities in post-implantation rat embryos cultured in vitro, and cranio-facial malformations in mouse fetuses. Ectopic maxillary cartilage has been also described as a typical FON-related malformation. This work studies the morphogenesis of the ectopic cartilage in rat embryos and fetuses exposed in vivo to FON during the early postimplantation period. METHODS: Pregnant rats were treated with 0, 250, and 500 mg/kg FON on Day 9.5 of pregnancy (D9.5) and sacrificed at term (D20), during the early fetal period (D17) or at different embryogenetic periods (D10, D11, D12). The skeleton was examined after stain of bone and cartilage or of cartilage alone respectively at term or at D17. The neural crest cell (NCC) migration and compaction was investigated at D10 and D11 and the cranial nerve organization described at D12. RESULTS: Triadimefon is teratogenic in rats under the chosen experimental conditions. The malformations were at the level of the cranio-facial and axial skeleton at term and of the hindbrain nerves in embryos. A NCC abnormal migration and compaction was observed at the level of the first branchial arch: in FON-exposed embryos NCC were detected at the level of both maxillary and mandibular processes, whereas control embryos showed the immunostained tissue only at the level of the mandibular bud. CONCLUSIONS: The pathogenic pathway, proposed to explain the ectopic cartilage, is the displacement of part of the NCC-derived tissues at the maxillary region of the first branchial arch.     

Plant Regeneration from Protoplasts of Talinum paniculatum

The protoplasts of Talinum paniculaturn (Jaeq.) Gaertn. were isolated from leaves and calli. The mesophyll protoplasts did not undergo normal division and lived one week at the longest in culture. However, the callus protoplasts, cultured in P4 medium (K8p+2, 4-D 0.2 mg/L, NAA 1.0 mg/L, ZT 0.5 mg/L, coconut milk 50 mL/L, glucose 0.5 mol/L), underwent first division after 3 d of culture. The division frequency was 36.7 % after 7 d of culture. The regeneration frequencies of callus were 0.31% in liquid culture and 0.34% in double-layer culture. Shoots differentiated on regeneration media and rooted on R3 and R7 media. Mature plants were obtained 2～3 months after transplanting the protoplast-derived plantlets into flower pot or successive subculturing in test tubes. The results also indicated that: (1) Too long a period of callus culture in liquid medium or in solid proliferation medium was unfavorable to differentiation. (2) Low concentration of 6-BA in medium was suitable for callus differentiation. (3) GA3 promoted development of young adventitious bud. (4) Multi-effect triazole significantly strengthened sprout and root development in test tube cultures.     

Enhancement of Peroxidase, Polyphenol Oxidase and Superoxide Dismutase Activities by Triadimefon in NaCl Stressed Raphanus Sativus L.

The activities of peroxidase, polyphenol oxidase and superoxide dismutase was significantly lower in roots and leaves of NaCl stressed radish (Raphanus sativus L.) plants. Addition of triadimefon to the NaCl stressed plants increased peroxidase, polyphenol oxidase and superoxide dismutase activities, and thereby ameliorated the negative effect of NaCl stress.     

Increased lymphocyte sister chromatid exchange frequency in workers with exposure to low level of ethylene dichloride

The genotoxicity of low-level exposure to ethylene dichloride (EDC) and vinyl chloride monomer (VCM) in humans is not clear. We used lymphocyte sister chromatid exchange (SCE) frequency as a parameter to investigate the genotoxicity of low level EDC and VCM in VCM-manufacturing workers. The SCE frequency was determined for 51 male workers with exposure to VCM and/or EDC and for 20 male workers devoid of such exposure. Epidemiological data were obtained by questionnaire, and included history of smoking, drinking, and any medication taken, as well as a detailed occupational history. Personal- and area-sampling and analysis were conducted in order to calculate the time-weighted average (TWA) contaminant-exposure level corresponding to different job categories. Moderate EDC exposure around 1 ppm corresponded to a significantly greater SCE frequency than was the case for the low EDC exposure group (p<0.01). However, VCM exposure of similar level was not associated with increased SCE. We conclude that EDC may cause genotoxicity at a relatively low level of exposure.     

Synthesis, structures and spectroscopic properties of new 1,2-bis[2-(4-methyl-7-acetylamino-1,8-naphthyridine)]ethylene ligand and its binuclear copper(I) complexes

The synthesis, characterization, spectroscopic properties of a new ligand 1,2-bis[2-(4-methyl-7-acetylamino-1,8-naphthyridine)]ethylene (L) and its two binuclear Cu(I) complexes containing triphenylphosphine (PPh₃) or bis(diphenylphosphino)methane (dppm), [Cu₂(L)(PPh₃)₄](BF₄)₂·2CH₂Cl₂ (1·2CH₂Cl₂) and [Cu₂(L)(dppm)₂](BF₄)₂·4H₂O (2·4H₂O) are reported. The structural investigation of these compounds based on X-ray crystal analysis shows that the copper(I) centers adopt different coordination geometries, O(N)CuP₂⁺ and NCuP₂⁺ for complexes 1 and 2, respectively. Upon irradiation of a degassed organic solution of L at 365 nm, photoinduced isomerization reaction and an intramolecular proton transfer of ligand L were detailed studied by absorption spectral changes. A spectroscopic investigation involving time-dependent density functional theory calculations allows assignment of the excited states that relate to emission and transient absorption spectra. The observed lower-energy absorption bands appearing in the region of 413 and 418 nm for 1 and 2 in dichloromethane are assigned to ligand-to-ligand charge transfer (LLCT, phosphine → napy) transition in nature. Compared with well-structured solid-state emission originating from ππ^∗ transition of ligand L, complexes 1 and 2 exhibit intense room-temperature solid-state emissions with λ_max at 586 and 620 nm, respectively. The energy and the shape of the emission bands are clearly different from that of the ligand, indicating the emissions come from different excited states.     

Vinyl-ruthenium entities as markers for intramolecular electron transfer processes

The present account summarizes our work on mononuclear vinyl ruthenium complexes of the type RuCl(CHCHR′)(CO)(PR₃)₂L, divinyl-bridged diruthenium complexes {RuCl(CO)(PR₃)₂L}₂(μ-CHCH-bridge-CHCH) and on heterobinuclear systems where only one of the two redox-active metal-organic moieties is of the vinyl ruthenium type. The favourable electrochemical properties of the {RuCl(CO)(PR₃)₂L(CHCH-) tag and the various spectroscopic handles offered by that unit provide detailed insights into the charge and spin delocalization over the {MCl(CO)(PR₃)₂L} and CHCHR′ constituents in their associated radical cations. They also offer a convenient means for measuring electronic coupling in the mixed-valent radical cations of the homo- and heterodinuclear vinyl-bridged complexes and, under favourable circumstances, on the rate of intramolecular electron transfer between the individual redox sites. Aspects of this work include examples of complexes showing time-dependent valence trapping, complexes aimed at delineating the efficiencies of through-space versus through-bond pathways for electron delocalization, complexes where electrostatic effects on the redox splitting ΔE_1/2 dominate over those from the resonance contribution and systems that exhibit extensive charge and spin delocalization between two dislike endgroups despite their intrinsically different redox potentials.     

Improved Lipid Visualization with a Modified Osmium Tetroxide Method Using Ultrasonic Treatment and Intensification with Imidazole or Triazole

Formalin fixed autopsy tissue containing lipids were cut into 1-5 nun thick blocks, washed well, then postfixed in 2% OsO₄ in 0.03 M veronal acetate buffer for 30, 60, 90, 120, or 180 min with or without ultrasonic treatment. Tissues exposed to ultrasound for 90 min showed superior penetration of OsO₄ and well preserved histological architecture. Tissues also were immersed for 1 hr in veronal acetate buffer (pH 7.4) containing 0.5% imidazole or triazole and compared with untreated controls. Paraffin sections, 4 μm thick, were examined under a light microscope with an image analyzer. Both intensity and percentage area of osmium blackening were significantly higher in samples immersed in imidazole or triazole than in untreated controls. No difference was observed between imidazole- and triazole-immersed samples. The OsO₄ method, modified by ultrasound treatment and imidazole- or triazole-immersion, can be applied to routine formalin fixed autopsy materials for improved lipid visualization.     

Design,Synthesis, and Antifungal Activities of Novel 1,2,4‐Triazole Schiff Base Derivatives

With the aim to find new compounds with high antifungal activity, 21 4‐amino‐5‐substituted‐1,2,4‐triazole Schiff bases ( 2a  –  2g , 3a  –  3g , and 4a  –  4g ) were designed and synthesized. Their antifungal activities against Pythium solani, Gibberlla nicotiancola, Fusarium oxysporium f. sp. niveum, Gibberlla saubinetii, Alternaria iycopersici, Phytophthora capsici, Physalospora piricola, Cercospora arachidicola hori, and Fusarium oxysporium f. sp. cucumber were tested, parts of the compounds exhibited excellent antifungal activity. This research provides useful information for further study of antifungal agents.     

Screening of bromotyramine analogues as antifouling compounds against marine bacteria

Rapid and efficient synthesis of 23 analogues inspired by bromotyramine derivatives, marine natural products, by means of CuSO₄-catalysed [3+2] alkyne–azide cycloaddition is described. The final target was then assayed for anti-biofilm activity against three Gram-negative marine bacteria, Pseudoalteromonas ulvae (TC14), Pseudoalteromonas lipolytica (TC8) and Paracoccus sp. (4M6). Most of the synthesised bromotyramine/triazole derivatives are more active than the parent natural products Moloka’iamine (A) and 3,5-dibromo-4-methoxy-β-phenethylamine (B) against biofilm formation by the three bacterial strains. Some of these compounds were shown to act as non-toxic inhibitors of biofilm development with EC₅₀ < 200 μM without any effect on bacterial growth even at high concentrations (200 μM).